1. Field of the Invention
The present invention relates to an illuminating device for a display device, a lamp supporting member, and a liquid crystal display device. More particularly, it relates to an illuminating device for a display device suitable for constituting a backlight of a transparent liquid crystal display device or a semi-transparent liquid crystal display device having a transparent region in a liquid crystal display element, a lamp supporting member which is used in the illuminating device for a display device, and a liquid crystal display device including the illuminating device for a display device.
2. Description of the Related Art
An illuminating device for a display device provides light to a device for displaying light and is widely used in a backlight part and the like in a liquid crystal display device, for example. That is, since a liquid crystal panel does not emit light by itself in the liquid crystal display device, the illuminating device for the display device is generally provided as the backlight part for emitting light to the liquid crystal panel in a transparent liquid crystal display device or a semi-transparent liquid crystal display device. Such a liquid crystal display device is indispensable for displaying information or screen images. High-quality products in which characteristics of the liquid crystal display such as low power consumption, lightweight, and thinness are sufficiently achieved have recently been utilized in display panels of consumer video monitors, industrial equipment monitors, Personal Digital Assistants and the like, and are widely applied to various fields.
As a backlight used in the liquid crystal display device, there are two types such as an edge light (side backlight) and a direct backlight.
As shown in FIG. 6, a structural characteristic of an edge light includes a bar-like light source 102 in a frame 103, such as a cold cathode fluorescent tube, disposed on a side surface of a transparent light guide plate 101. In this case, light from the light source 102 is made incident to the light guide plate 101 and is then outputted from the light guide plate 101 through an optical sheet 104 to the liquid crystal panel 105 by a frosting, a printing, or a prism and the like of the light guide plate 101. Thus, the liquid crystal display device may become thinner, but an increase in the number of the light sources 102 to increase the luminance has a direct influence on the thickness of a module. In addition, since a heavy continuum such as an acrylic compound is used for the light guide plate 101, the larger the liquid crystal display device becomes beyond a 20-inch model, the heavier the model becomes using the liquid crystal displace device.
As shown in FIG. 7, in the case of a direct backlight, a plurality of bar-like light sources 113, such as cold cathode fluorescent tubes, are provided on the back surface of a display element 117 such as a liquid crystal panel. In this case, light from the bar-like light sources 113 is almost directly incident to the display element 117, and in many cases a diffuser 115 is provided between the display element 117 and the bar-like light source 113 in order to diffuse the images of the bar-like light source 113. Additionally, 118 indicates a frame, 116 optical sheets, 114 a lamp frame, 112 a highly reflective resin, and 111 a backlight frame. Thus, many light sources 113 can be arranged to increase the amount of light, and light loss is small because the light is directly incident to the display element 117, and a large size beyond 20-inch models can be easily achieved. However, the number of parts is increased because of the large number of the light sources 113, and a circuit for driving the light sources 113 also becomes large. In addition, power consumption and the total amount of generated heat is increased.
Such liquid crystal displays are advanced in the field of small-sized display elements, and advances in the market for displays in laptop personal computers (PC) and mobile phones have been developed. In these fields, the display size is mainly below a 15-inch model and a slim shape is indispensable, so that the edge light is selected in view of merchantability.
Presently, liquid crystal display devices have been dramatically enlarged because of the completion of a process using a larger mother glass, so that the liquid crystal display devices may be used in televisions (20-inch models to 50-inch models) for home use. In such televisions, brightness becomes more important as a basic performance characteristic than in PCs and mobile phones. For example, while a luminance specification is generally about 250 candela (cd/m2) in PC monitors, the luminance specification must be 500 candela (cd/m2) or more for televisions. In this respect, the direct backlight is preferable in order to provide a large backlight having a high luminance.
In an illuminating device for a display device which may be used in a conventional liquid crystal display device and the like, there is a lamp holder which is formed in a segmented gripping shape having an opening in one portion and made of a flexible transparent material (see, for example, pages 1-2 and 4 in Japanese Kokai Publication 2001-210126); a backlight assembly including a plurality of lamps having sub lamps, and a lamp holder for housing a connection part via which the sub lamps are connected to each other (see, for example, pages 1-2, 7, and 13 in Japanese Kokai Publication 2004-55531); a backlight device in which a reflector for condensing light emitted from a light source in a light guide plate is formed of metal and supports the light source (see, for example, pages 1-2 in Japanese Kokai Patent Publication Hei-10-207406); a fluorescent lamp unit in which a fluorescent lamp is housed in a trough-shaped unit support, and a lamp support including a translucent or light reflective synthetic resin arranged between the fluorescent lamp and the unit support (see, for example, pages 1-2 in Japanese Kokai Patent Publication Hei-09-330613). In addition, US 2003/0227767 A1 is incorporated by Japanese Kokai Publication 2004-55531 by reference.
According to the conventional lamp holder, since a pin for fixing the lamp holder is provided just under a fluorescent tube, light from the fluorescent tube leaks through the pin, which results in a reduction of the luminance at that portion (see, for example, FIG. 2 of Japanese Kokai Patent Publication 2001-210126). Also, in a configuration in which the lamp holder is bonded to a base bottom surface by a bonding projection and a bonding groove, light leaks from the bonding projection provided just under the lamp (see, for example, FIG. 5 of Japanese Kokai Patent Publication 2004-55531). In these devices, a lower luminance and an uneven luminance are created due to the structure of the lamp holder. For example, when the amount of light is small at the time of carrying out gradation of the display or starting the display, the uneven luminance is likely to become conspicuous, and therefore an improvement in this field is needed. Especially in the field of liquid crystal displays, since a large illuminating device having high luminance and low cost is needed in order to improve the merchantability, it is necessary to provide a product having high quality and high merchantability by reducing the influence of the lamp holder on the luminance and preventing a reduction of the display quality. Therefore, there is room for improvement to reduce uneven luminance occurring due to the structure of the lamp holder in the illuminating device for a display device in which high quality is needed.